Solar power is the conversion of energy from
sunlight into
electricity
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describe ...
, either directly using
photovoltaics
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...
(PV) or indirectly using
concentrated solar power.
Photovoltaic cells convert light into an
electric current using the
photovoltaic effect. Concentrated solar power systems use
lenses or mirrors and
solar tracking systems to focus a large area of sunlight to a hot spot, often to drive a
steam turbine
A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam tu ...
.
Photovoltaics were initially solely used as a source of electricity for small and medium-sized applications, from the
calculator
An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics.
The first solid-state electronic calculator was created in the early 1960s. Pocket-sized ...
powered by a single solar cell to remote homes powered by an
off-grid
Off-the-grid or off-grid is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities. The term "off-the-grid" traditionally refers to not being connected to the electrical g ...
rooftop PV system. Commercial concentrated solar power plants were first developed in the 1980s. Since then, as the cost of solar electricity has fallen, grid-connected
solar PV systems have
grown more or less exponentially. Millions of installations and gigawatt-scale
photovoltaic power stations continue to be built, with half of new generation capacity being solar in 2021.
As of 2021, solar generates 4% of the world's electricity, compared to 1% in 2015 when the
Paris Agreement to
limit climate change was signed.
Along with
onshore wind, the cheapest
levelised cost of electricity is
utility-scale solar.
Much more
low carbon power
Low-carbon power is electricity produced with substantially lower greenhouse gas emissions than conventional fossil fuel power generation. The energy transition to low-carbon power is one of the most important actions required to limit climat ...
, such as solar, is urgently needed to
limit climate change, but the
International Energy Agency
The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organisation, established in 1974, that provides policy recommendations, analysis and data on the entire global energy sector, with a recent focus on curbing car ...
said in 2022 that more effort was needed for grid integration and the mitigation of policy, regulation and financing challenges.
Technologies
Solar power plants use one of two technologies:
*
Photovoltaic (PV)
systems
A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and expresse ...
use
solar panels, either on
rooftops or in ground-mounted
solar farms, converting sunlight directly into electric power.
*
Concentrated solar power (CSP) uses mirrors or lenses to concentrate sunlight to extreme heat to eventually make steam, which is converted into electricity by a
turbine.
Photovoltaic cells
A
solar cell, or photovoltaic cell, is a device that converts light into electric current using the
photovoltaic effect. The first solar cell was constructed by
Charles Fritts in the 1880s. The German industrialist
Ernst Werner von Siemens was among those who recognized the importance of this discovery. In 1931, the German engineer Bruno Lange developed a photo cell using
silver selenide
Silver selenide (Ag2Se) is the reaction product formed when selenium toning analog silver gelatine photo papers in photographic print toning. The selenium toner contains sodium selenite (Na2SeO3) as one of its active ingredients, which is the sourc ...
in place of
copper oxide, although the prototype
selenium cells converted less than 1% of incident light into electricity. Following the work of
Russell Ohl in the 1940s, researchers Gerald Pearson,
Calvin Fuller
Calvin Souther Fuller (May 25, 1902 – October 28, 1994) was an American physical chemist at AT&T Bell Laboratories where he worked for 37 years from 1930 to 1967. Fuller was part of a team in basic research that found answers to physical ch ...
and Daryl Chapin created the
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
solar cell in 1954. These early solar cells cost US$286/watt and reached efficiencies of 4.5–6%. In 1957,
Mohamed M. Atalla developed the process of silicon
surface passivation by
thermal oxidation at
Bell Labs
Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984),
then AT&T Bell Laboratories (1984–1996)
and Bell Labs Innovations (1996–2007),
is an American industrial research and scientific development company owned by mul ...
.
The surface passivation process has since been critical to
solar cell efficiency.
over 90% of the market is
crystalline silicon.
The array of a
photovoltaic system, or PV system, produces
direct current
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or ev ...
(DC) power which fluctuates with the sunlight's intensity.
For practical use this usually requires conversion to
alternating current
Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
(AC), through the use of
inverters.
Multiple solar cells are connected inside panels.
Panels are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC, the desired frequency/phase.
Many residential PV systems are connected to the grid wherever available, especially in developed countries with large markets.
In these
grid-connected PV systems, use of energy storage is optional.
In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such
stand-alone power system
A stand-alone power system (SAPS or SPS), also known as remote area power supply (RAPS), is an off-the-grid electricity system for locations that are not fitted with an electricity distribution system. Typical SAPS include one or more methods of e ...
s permit operations at night and at other times of limited sunlight.
Concentrated solar power
Concentrated solar power (CSP), also called "concentrated solar thermal", uses lenses or mirrors and tracking systems to concentrate sunlight, then use the resulting heat to generate electricity from conventional steam-driven turbines.
A wide range of concentrating technologies exists: among the best known are the
parabolic trough
A parabolic trough is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The sunlight which enters the mirror parallel to its plane of symmetry is ...
, the
compact linear Fresnel reflector, the
dish Stirling and the
solar power tower. Various techniques are used to track the sun and focus light. In all of these systems a
working fluid
For fluid power, a working fluid is a gas or liquid that primarily transfers force, motion, or mechanical energy. In hydraulics, water or hydraulic fluid transfers force between hydraulic components such as hydraulic pumps, hydraulic cylinders, a ...
is heated by the concentrated sunlight, and is then used for power generation or energy storage.
[Martin and Goswami (2005), p. 45] Thermal storage efficiently allows overnight electricity generation, thus complementing PV. CSP generates a very small share of solar power and in 2022 the IEA said that CSP should be better paid for its storage.
the LCOE of CSP is over twice that of PV, however their very high temperatures may prove useful to help decarbonize industries (perhaps via hydrogen) which need to be hotter than electricity can provide.
Hybrid systems
A hybrid system combines solar with energy storage and/or one or more other forms of generation. Hydro, wind and batteries are commonly combined with solar. The combined generation may enable the system to vary power output with demand, or at least smooth the solar power fluctuation. There is a lot of hydro worldwide, and adding solar panels on or around existing hydro reservoirs is particularly useful, because hydro is usually more flexible than wind and cheaper at scale than batteries, and existing power lines can sometimes be used.
Development and deployment
Early days
The early development of solar technologies starting in the 1860s was driven by an expectation that coal would soon become scarce, such as experiments by
Augustin Mouchot
Augustin Mouchot (; ; 7 April 1825 – 4 October 1912) was a 19th-century France, French inventor of the earliest solar-powered engine, converting solar energy into mechanical steam power.
Background
Mouchot was born in Semur-en-Auxois, France ...
.
Charles Fritts installed the world's first rooftop photovoltaic solar array, using 1%-efficient
selenium cells, on a New York City roof in 1884. However, development of solar technologies stagnated in the early 20th century in the face of the increasing availability, economy, and utility of coal and
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
. The first satellite with solar panels
was launched in 1957.
[ ]
By the 1970s, solar power was being used on
satellites, but the cost of solar power was considered to be unrealistic for conventional applications.
In 1974 it was estimated that only six private homes in all of North America were entirely heated or cooled by functional solar power systems. However, the
1973 oil embargo
The 1973 oil crisis or first oil crisis began in October 1973 when the members of the Organization of Arab Petroleum Exporting Countries (OAPEC), led by Saudi Arabia, proclaimed an oil embargo. The embargo was targeted at nations that had sup ...
and
1979 energy crisis
The 1979 oil crisis, also known as the 1979 Oil Shock or Second Oil Crisis, was an energy crisis caused by a drop in oil production in the wake of the Iranian Revolution. Although the global oil supply only decreased by approximately four pe ...
caused a reorganization of energy policies around the world and brought renewed attention to developing solar technologies.
Deployment strategies focused on incentive programs such as the Federal Photovoltaic Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the formation of research facilities in the United States (SERI, now
NREL), Japan (
NEDO), and Germany (
Fraunhofer ISE).
Between 1970 and 1983 installations of photovoltaic systems grew rapidly. In the United States, President
Jimmy Carter
James Earl Carter Jr. (born October 1, 1924) is an American politician who served as the 39th president of the United States from 1977 to 1981. A member of the Democratic Party (United States), Democratic Party, he previously served as th ...
set a target of producing 20% of U.S. energy from solar by the year 2000, but his successor,
Ronald Reagan, removed the funding for research into renewables.
Falling oil prices in the early 1980s moderated the
growth of photovoltaics from 1984 to 1996.
Mid-1990s to 2010
In the mid-1990s development of both, residential and commercial
rooftop solar
A rooftop solar power system, or rooftop PV system, is a photovoltaic (PV) system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a syste ...
as well as utility-scale
photovoltaic power stations began to accelerate again due to supply issues with oil and natural gas,
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
concerns, and the improving economic position of PV relative to other energy technologies.
In the early 2000s, the adoption of
feed-in tariffs—a policy mechanism, that gives renewables priority on the grid and defines a fixed price for the generated electricity—led to a high level of investment security and to a soaring number of PV deployments in Europe.
2010s
For several years, worldwide growth of solar PV was driven by
European deployment, but then shifted to Asia, especially
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
and
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
, and to a growing number of countries and regions all over the world. The largest manufacturers were located in China. Although concentrated solar power grew more than tenfold it remained a tiny proportion of the total,
[
] because the cost of utility-scale solar PV fell by 85%, to below CSP cost which fell only 68%.
2020s
Despite the rising cost of materials, such as
polysilicon
Polycrystalline silicon, or multicrystalline silicon, also called polysilicon, poly-Si, or mc-Si, is a high purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry.
Polysilicon is produce ...
, during the
2021–2022 global energy crisis; the cost of some other energy sources, such as natural gas, rose more thus making
utility scale solar the cheapest energy source in many countries. 1 TW had been installed by 2022. However growth continued to be hindered by
fossil-fuel subsidies.
Current status
About half of installed capacity is utility scale.
According to the IEA not enough CSP is being built.
Forecasts
Most new renewable capacity between 2022 and 2027 is forecast to be solar, surpassing coal as the largest source of installed power capacity.
Utility scale is forecast to become the largest capacity in all regions except
sub-Saharan Africa
Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...
.
According to a 2021 study global electricity generation potential of
rooftop solar
A rooftop solar power system, or rooftop PV system, is a photovoltaic (PV) system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a syste ...
panels is estimated at 27 PWh per year at cost ranging from $40 (Asia) to $240 per MWh (US, Europe). Its practical realization will however depend on the availability and cost of scalable electricity storage solutions.
Photovoltaic power stations
Concentrating solar power stations
Commercial concentrating solar power (CSP) plants, also called "solar thermal power stations", were first developed in the 1980s. The 377 MW
Ivanpah Solar Power Facility, located in California's Mojave Desert, is the world's largest solar thermal power plant project. Other large CSP plants include the
Solnova Solar Power Station (150 MW), the
Andasol solar power station (150 MW), and
Extresol Solar Power Station (150 MW), all in Spain. The principal advantage of CSP is the ability to efficiently add thermal storage, allowing the dispatching of electricity over up to a 24-hour period. Since peak electricity demand typically occurs at about 5 pm, many CSP power plants use 3 to 5 hours of thermal storage.
Economics
Cost per watt
The typical cost factors for solar power include the costs of the modules, the frame to hold them, wiring, inverters, labour cost, any land that might be required, the grid connection, maintenance and the solar insolation that location will receive.
Photovoltaic systems use no fuel, and modules typically last 25 to 40 years. Thus upfront capital and financing costs make up 80 to 90% of the cost of solar power.
Some countries are considering
price caps, whereas others prefer
contracts for difference.
Installation prices
Expenses of high power band solar modules has greatly decreased over time. Beginning in 1982, the cost per kW was approximately 27,000 American dollars, and in 2006 the cost dropped to approximately 4,000 American dollars per kW. The PV system in 1992 cost approximately 16,000 American dollars per kW and it dropped to approximately 6,000 American dollars per kW in 2008.
In 2021 in the US, residential solar cost from 2 to 4 dollars/watt (but solar shingles cost much more) and utility solar costs were around $1/watt.
Productivity by location
The productivity of solar power in a region depends on
solar irradiance, which varies through the day and year and is influenced by
latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...
and
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
.
PV system output power also depends on ambient temperature, wind speed, solar spectrum, the local
soiling conditions, and other factors.
Onshore
wind power tends to be the cheapest source of electricity in Northern Eurasia, Canada, some parts of the United States, and
Patagonia in Argentina: whereas in other parts of the world mostly solar power (or less often a combination of wind, solar and other low carbon energy) is thought to be best.
The locations with highest annual solar irradiance lie in the arid tropics and subtropics. Deserts lying in low latitudes usually have few clouds, and can receive sunshine for more than ten hours a day. These hot deserts form the ''Global Sun Belt'' circling the world. This belt consists of extensive swathes of land in
Northern Africa,
Southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number o ...
,
Southwest Asia,
Middle East
The Middle East ( ar, الشرق الأوسط, ISO 233: ) is a geopolitical region commonly encompassing Arabian Peninsula, Arabia (including the Arabian Peninsula and Bahrain), Anatolia, Asia Minor (Asian part of Turkey except Hatay Pro ...
, and
Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
, as well as the much smaller deserts of
North
North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography.
Etymology
The word ''north ...
and
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
.
So solar is (or is predicted to become) the cheapest source of energy in all of Central America, Africa, the Middle East, India, South-east Asia, Australia, and several other places.
Different measurements of
solar irradiance (direct normal irradiance, global horizontal irradiance) are mapped below :
File:SolarGIS-Solar-map-North-America-en.png, North America
File:SolarGIS-Solar-map-Latin-America-en.png, South America
File:SolarGIS-Solar-map-Europe-en.png, Europe
File:SolarGIS-Solar-map-Africa-and-Middle-East-en.png, Africa and Middle East
File:SolarGIS-Solar-map-South-And-South-East-Asia-en.png, South and South-East Asia
File:SolarGIS-Solar-map-Australia-en.png, Australia
File:SolarGIS-Solar-map-World-map-en.png, World
Self consumption
In cases of self-consumption of solar energy, the payback time is calculated based on how much electricity is not purchased from the grid. However, in many cases, the patterns of generation and consumption do not coincide, and some or all of the energy is fed back into the grid. The electricity is sold, and at other times when energy is taken from the grid, electricity is bought. The relative costs and prices obtained affect the economics. In many markets, the price paid for sold PV electricity is significantly lower than the price of bought electricity, which incentivizes self consumption.
Moreover, separate self consumption incentives have been used in e.g. Germany and Italy.
Grid interaction regulation has also included limitations of grid feed-in in some regions in Germany with high amounts of installed PV capacity.
By increasing self consumption, the grid feed-in can be limited without
curtailment, which wastes electricity.
A good match between generation and consumption is key for high self-consumption. The match can be improved with batteries or controllable electricity consumption.
However, batteries are expensive and profitability may require the provision of other services from them besides self consumption increase.
Hot water storage tanks with electric heating with heat pumps or resistance heaters can provide low-cost storage for self consumption of solar power.
Shiftable loads, such as dishwashers, tumble dryers and washing machines, can provide controllable consumption with only a limited effect on the users, but their effect on self-consumption of solar power may be limited.
Energy pricing, incentives and taxes
The original political purpose of incentive policies for PV was to facilitate an initial small-scale deployment to begin to grow the industry, even where the cost of PV was significantly above grid parity, to allow the industry to achieve the economies of scale necessary to reach grid parity. Since reaching grid parity some policies are implemented to promote national energy independence,
high tech job creation and reduction of CO
2 emissions.
Three incentive mechanisms are often used in combination as investment subsidies: the authorities refund part of the cost of installation of the system, the electricity utility buys PV electricity from the producer under a multiyear contract at a guaranteed rate, and
Solar Renewable Energy Certificates
Solar Renewable Energy Certificates (SRECs) or Solar Renewable Energy Credits are a form of Renewable Energy Certificate or "Green tag" existing in the United States of America. SRECs exist in states that have Renewable Portfolio Standard (RPS) ...
(SRECs).
Financial incentives for photovoltaics differ across countries, including
Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
,
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
,
Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwee ...
,
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
,
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
, and the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
and even across states within the US.
Net metering
In
net metering the price of the electricity produced is the same as the price supplied to the consumer, and the consumer is billed on the difference between production and consumption. Net metering can usually be done with no changes to standard
electricity meters, which accurately measure power in both directions and automatically report the difference, and because it allows homeowners and businesses to generate electricity at a different time from consumption, effectively using the grid as a giant storage battery. With net metering, deficits are billed each month while surpluses are rolled over to the following month. Best practices call for perpetual roll over of kWh credits. Excess credits upon termination of service are either lost or paid for at a rate ranging from wholesale to retail rate or above, as can be excess annual credits.
Taxes
In some countries
tariffs (import taxes) are imposed on imported solar panels.
Grid integration
The overwhelming majority of electricity produced worldwide is used immediately because traditional generators can adapt to demand and storage is usually more expensive. Both solar power and
wind power are
sources of variable renewable power, meaning that all available output must be used locally, carried on
transmission lines elsewhere to be used, or stored (e.g. in a battery). Since solar energy is not available at night, storing its energy is potentially an important issue particularly in off-grid and for future
100% renewable energy
100% renewable energy means getting all energy from renewable resources. The endeavor to use 100% renewable energy for electricity, heating, cooling and transport is motivated by climate change, pollution and other environmental issue ...
scenarios to have continuous electricity availability.
Solar electricity is inherently variable but
somewhat predictable by time of day, location, and seasons. Solar is intermittent due to day/night cycles and unpredictable weather. How much of a special challenge solar power is in any given electric utility varies significantly. In places with hot summers and mild winters, solar is well matched to daytime cooling demands.
Conventional hydroelectric dams work very well in conjunction with solar power; water can be held back or released from a reservoir as required. Where suitable geography is not available,
pumped-storage hydroelectricity can use solar power to pump water to a high reservoir on sunny days, then the energy is recovered at night and in bad weather by releasing water via a hydroelectric plant to a low reservoir where the cycle can begin again.
Energy storage
Concentrated solar power plants may use
thermal storage
Thermal energy storage (TES) is achieved with widely different technologies. Depending on the specific technology, it allows excess thermal energy to be stored and used hours, days, months later, at scales ranging from the individual process, ...
to store solar energy, such as in high-temperature molten salts. These salts are an effective storage medium because they are low-cost, have a high specific heat capacity, and can deliver heat at temperatures compatible with conventional power systems. This method of energy storage is used, for example, by the
Solar Two power station, allowing it to store 1.44
TJ in its 68 m
3 storage tank, enough to provide full output for close to 39 hours, with an efficiency of about 99%.
In
stand alone PV systems batteries
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
are traditionally used to store excess electricity. With
grid-connected photovoltaic power system, excess electricity can be sent to the
electrical grid.
Net metering and
feed-in tariff programs give these systems a credit for the electricity they produce. This credit offsets electricity provided from the grid when the system cannot meet demand, effectively trading with the grid instead of storing excess electricity.
When wind and solar are a small fraction of the grid power, other generation techniques can adjust their output appropriately, but as these forms of variable power grow, additional balance on the grid is needed. As prices are rapidly declining, PV systems increasingly use rechargeable batteries to store a surplus to be later used at night.
Batteries used for grid-storage can stabilize the
electrical grid by
leveling out peak loads for a few hours. In the future, less expensive batteries could play an important role on the electrical grid, as they can charge during periods when generation exceeds demand and feed their stored energy into the grid when demand is higher than generation.
Common battery technologies used in today's home PV systems include
nickel-cadmium,
lead-acid,
nickel metal hydride
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to r ...
, and
lithium-ion
A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also ...
.
Lithium-ion batteries have the potential to replace lead-acid batteries in the near future, as they are being intensively developed and lower prices are expected due to
economies of scale
In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of time. A decrease in cost per unit of output enables ...
provided by large production facilities such as the
Gigafactory 1. In addition, the Li-ion batteries of plug-in
electric car
An electric car, battery electric car, or all-electric car is an automobile that is propelled by one or more electric motors, using only energy stored in batteries. Compared to internal combustion engine (ICE) vehicles, electric cars are quiet ...
s may serve as future storage devices in a
vehicle-to-grid system. Since most vehicles are parked an average of 95% of the time, their batteries could be used to let electricity flow from the car to the power lines and back. Other rechargeable batteries used for
distributed PV systems include,
sodium–sulfur and
vanadium redox batteries, two prominent types of a
molten salt and a
flow
Flow may refer to:
Science and technology
* Fluid flow, the motion of a gas or liquid
* Flow (geomorphology), a type of mass wasting or slope movement in geomorphology
* Flow (mathematics), a group action of the real numbers on a set
* Flow (psyc ...
battery, respectively.
Other technologies
In an electricity system without
grid energy storage
Grid energy storage (also called large-scale energy storage) is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inex ...
, generation from stored fuels (coal, biomass, natural gas, nuclear) must go up and down in reaction to the rise and fall of solar electricity (see
load following power plant). While hydroelectric and natural gas plants can quickly respond to changes in load, coal, biomass and nuclear plants usually take considerable time to respond to load and can only be scheduled to follow the predictable variation. Depending on local circumstances, beyond about 20–40% of total generation, grid-connected
intermittent sources like solar tend to require investment in some combination of
grid interconnections,
energy storage or
demand side management. In countries with high solar generation, such as Australia and Germany, electricity prices have been known to go negative in the middle of the day when solar is generating a lot of power, thus incentivizing new
battery storage.
The combination of wind and solar PV has the advantage that the two sources complement each other because the peak operating times for each system occur at different times of the day and year. The power generation of such
solar hybrid power systems is therefore more constant and fluctuates less than each of the two component subsystems.
Solar power is seasonal, particularly in northern/southern climates, away from the equator, suggesting a need for long term seasonal storage in a medium such as hydrogen or pumped hydroelectric.
Environmental effects
A very small proportion of solar power is
concentrated solar power. Concentrated solar power may use much more water than gas-fired power. This can be a problem, as this type of solar power needs strong sunlight so is often built in deserts.
Solar power is cleaner than electricity from
fossil fuels:
solar power does not lead to any harmful emissions during operation, but the production of the panels leads to some amount of pollution. A 2021 study estimated the carbon footprint of manufacturing monocrystalline panels at 515 g CO2/kWp in the US and 740 g CO2/kWp in China, but this is expected to fall as manufacturers use more clean electricity and recycled materials.
Solar power carries an upfront cost to the environment via production with a carbon payback time of a few years ,
but offers clean energy for the rest of its 30 year lifetime.
The
life-cycle greenhouse-gas emissions of solar farms are less than 50 gram (g) per
kilowatt-hour (kWh),
but with
battery storage could be up to 150 g/kWh. In contrast, a
combined cycle gas-fired power plant without
carbon capture and storage emits around 500 g/kWh, and a coal-fired power plant about 1000 g/kWh. Similar to all energy sources where their total life cycle emissions are mostly from construction, the switch to
low carbon power
Low-carbon power is electricity produced with substantially lower greenhouse gas emissions than conventional fossil fuel power generation. The energy transition to low-carbon power is one of the most important actions required to limit climat ...
in the manufacturing and transportation of solar devices would further reduce carbon emissions.
Life-cycle
surface power density of solar power varies a lot
but averages about 7 W/m2, compared to about 240 for
nuclear power
Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced b ...
and 480 for gas. However when the land required for gas extraction and processing is accounted for gas power is estimated to have not much higher power density than solar.
PV requires much larger amounts of land surface to produce the same nominal amount of energy as sources with higher surface power density and capacity factor. According to a 2021 study, obtaining 25 to 80% of electricity from solar farms in their own territory by 2050 would require the panels to cover land ranging from 0.5 to 2.8% of the
European Union
The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are located primarily in Europe, Europe. The union has a total area of ...
, 0.3 to 1.4% in
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
, and 1.2 to 5.2% in
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
and
South Korea
South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...
. Occupation of such large areas for PV farms could drive residential opposition as well as lead to deforestation, removal of vegetation and conversion of farm land. However some countries, such as South Korea and Japan, use land for
agriculture under PV, or floating solar. Worldwide land use has minimal ecological impact. Land use can be reduced to the level of gas power by installing on buildings and other built up areas.
Harmful materials are used in the production of solar panels, but in generally in small amounts. the environmental impact of perovskite is hard to estimate, but there is some concern that
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
may become a problem.
A 2021
International Energy Agency
The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organisation, established in 1974, that provides policy recommendations, analysis and data on the entire global energy sector, with a recent focus on curbing car ...
study projects the demand for
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
will double by 2040. The study cautions that supply needs to increase rapidly to match demand from large-scale deployment of solar and required grid upgrades. More
tellurium
Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionall ...
and
indium may also be needed and recycling may help.
As solar panels are sometimes replaced with more efficient panels, the second-hand panels are sometimes reused in developing countries, for example in
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
. Several countries have specific regulations for the
recycling of solar panels. Although maintenance cost is already low compared to other energy sources, some academics have called for solar power systems to be designed to be more
repairable.
Political issues
over 40% of global polysilicon manufacturing capacity is in
Xinjiang
Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwes ...
in
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
, which raises concerns about human rights violations (
Xinjang internment camps) as well as supply chain dependency. However solar cannot be cut off, unlike oil and gas, so can contribute to
energy security.
See also
*
100% renewable energy
100% renewable energy means getting all energy from renewable resources. The endeavor to use 100% renewable energy for electricity, heating, cooling and transport is motivated by climate change, pollution and other environmental issue ...
*
Cost of electricity by source
*
Index of solar energy articles
*
List of cities by sunshine duration
*
List of photovoltaic power stations
*
List of solar thermal power stations
This is a list of the largest facilities generating electricity through the use of solar thermal power, specifically concentrated solar power.
Operational
Under construction
Announced
Cancelled
Decommissioned
* Eurelios ...
*
Renewable energy commercialization
*
Solar energy
*
Solar lamp
*
Solar vehicle
*
Sustainable energy
*
Timeline of solar cells
References
Further reading
*
External links
Solar energy and the environmentat
U.S. Energy Information Administration
The U.S. Energy Information Administration (EIA) is a principal agency of the U.S. Federal Statistical System responsible for collecting, analyzing, and disseminating energy information to promote sound policymaking, efficient markets, and publ ...
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Bright green environmentalism
Energy conversion
Sustainable energy
Power
Renewable energy